This invention relates to the remote copy of data between two storage systems that are situated at a geographic distance from, and coupled to, each other. When the data of one storage system is updated, the updated contents are transferred, or remotely copied, to the other storage system so that both systems have the same data. More specifically, this invention relates to a technique for effecting the copying of data by a remote copy function in a file system.
Methods for effecting remote copy of data between storage systems are known (see, for example, U.S. Pat. No. 6,442,551 and Japanese Unexamined Patent Publication No. 2003-76592). According to these methods, when the data of a disk drive at a certain location (a local site) is updated, the updated contents are transferred to a disk drive at another location (a remote site) so that the two disk drives have the same data.
According to the method disclosed in U.S. Pat. No. 6,442,551 and Japanese Unexamined Patent Publication No. 2003-76592, the storage system at a remote site is used as a standby system; i.e., when the local site becomes inaccessible, the storage system at the remote site is used as a file system.